Warming Arctic waters and depleting sea ice are making it easier for killer whales to swim ever northward in search of new sources of prey, including other species of whales, a new study says.

The killer whale's immense dorsal fin impedes it from surfacing in heavy sea ice. But as that ice disappears, the orcas have been seen hunting further north than ever before.

By:Kenyon WallaceToronto Star, Published on Mon Jan 30 2012

Warming Arctic waters and depleting sea ice are making it easier for killer whales to swim ever northward in search of sources of prey, including other species of whales, a new study has found.

After spending three years interviewing more than 100 Inuit hunters from 11 different Nunavut communities, researchers from Fisheries and Oceans Canada and the University of Manitoba believe killer whales, also known as orcas, are increasingly targeting prey in northern areas where they didn’t previously .

“Killer whales have been seen more and further into the Canadian Arctic, and when they go there, they eat,” said Steven Ferguson, a marine biologist with Fisheries and Oceans Canada and co-author of the study, published Monday in the online journal Aquatic Biosystems.

“Now it looks like some species might be depleted due to predation by killer whales. That’s something we didn’t expect.”

Inuit hunters interviewed for the study reported seeing more killer whales targeting narwhals, belugas and bowhead whales, which often grow much larger than orcas. Sightings were reported as far north as Foxe Basin, north of Hudson Bay, and Lancaster Sound, between Devon and Baffin Islands.

Killer whales, which lack natural predators, inhabit most of the world’s oceans, including the Arctic and Antarctic.

Ferguson says some hunters fear they may soon have to compete with killer whales for seal and whale meat as Arctic waters become more navigable for the orcas.

Whales that primarily live in the Arctic, such as narwhals and belugas, don’t have dorsal fins. That lets them surface easily for air in icy waters. Killer whales, which have large dorsal fins, couldn’t do that — until the warmer environment led to less sea ice.

“These ice-adapted whales and seals are not only food for the Inuit but also part of their culture. So it’s important that they maintain that connection to the environment,” Ferguson said.

“The Inuit don’t want to hunt humpback whales or minke whales, with which they don’t have a cultural history and don’t have a taste for.”

Jeff Higdon, a consulting wildlife scientist and co-author of the study, stressed researchers don’t have proof yet that killer whale populations in the Arctic are increasing. Rather, there are more observed instances of orcas preying on other whales in more northerly climes.

“The observations by Inuit hunters are highly accurate,” he said. “There’s no way we could recreate the information we get from local observers who have spent their lives out on the water.”

Higdon surmised that a resurgence of the bowhead population in the Foxe Basin since commercial whaling ended several decades ago may have also attracted killer whales.

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